Fluid pump having multiple impellers



United States Patent 3,391,858 FLUID PUMP HAVING MULTIPLE IMPELLERS Warren Heathcote De Lancey, 4205 S. Murray Ridge Road, Elyria, Ohio 44035 Filed Aug. 4, 1966, Ser. No. 570,301 9 Claims. (Cl. 230-108) ABSTRACT OF THE DISCLOSURE This invention relates to fluid pumps, especially centrifugal compressors wherein a liquid impellant is circulated in a closed cycle to entrain or gather secondary fluid and impart kinetic energy thereto. In such compressors the energized fluid separates from the liquid impellant in a high pressure collection chamber communicating with the compressor outlet; the liquid impellant returns to the inlet of the centrifugal impeller wheel for re-use in entraining or gathering additional fluid. A feature of the invention is that two impellers are used instead of one. One impeller pumps spend liquid up to a high static pressure; the other impeller receives the high pressure liquid and puts additional kinetic energy into it, thus causing it to entrain greater quantities of fluid than would otherwise be possible.

Background As described in United States Patent No. 3,081,932, the liquid impeller may be constructed with outwardly narrowing passages between the impeller vanes to form a venturi-like discharge from the impeller wheel, the objective being to provide high radial velocities out of the wheel. The high velocity liquid may be sprayed across a circumferential gap into an outwardly radiating diffuser passageway. As the liquid moves into the diffuser passageway it tends to expand and/or decelerate, although its momentum precludes substantial deceleration. In order for the liquid to fill the diffuser passageway it must draw in additional fluid along its boundary layers. This additional secondary fluid, for example refrigerant gas, can be taken from a second source adjacent the aforementioned circumferential gap. In effect the fast-moving liquid exerts a suction action on the gas to draw the gas into the liquid stream, as more particularly described in the aforementioned US. Patent No. 3,081,932.

One object of the present invention is to provide a pump wherein the liquid impellant is subjected to two pumping actions by two separate impellers, thus giving higher liquid velocities, increased fluid mixing or entrainment, greater energy exchange with the secondary fluid, and higher output pressures.

A further object is to provide a multiple impeller pump of the fluid entrainment or mixer type, wherein one of the impellers serves both as a pressure elevation mechanism and also as a fluid-separator for separating the recirculatin g fluid from the output fluid.

Another object is to provide a pump wherein the pumped liquid and mixed fluid are allowed to controllably expand or diffuse in an annular diffusion passageway which minimizes turbulence losses.

A further object is to provide a pump wherein the spent liquid impellant is pumped to a relatively high pressure by an auxiliary impeller, and thence returned to the fluidentraining impeller through an annular diffusion duct which efficiently converts velocity energy into pressure energy without excessive losses.

An additional object is to provide a pump wherein two impellers and two annular connecting diffusion passages are compactly nested within one another in a relatively small size housing.

3,391,858 Patented July 9, 1968 ice A general object is to provide a pump having desired features of small size, minimum number of moving parts, large dimensional tolerances on interfitting parts, low noise level operation, low starting torque, self-lubrication, freedom from vibration, easily controlled output pressure, ability to handle a variety of fluids having a large solid or liquid impurity content, built-in motor cooling for prevention of hot spots and attainment of higher motor loadings, low tooling cost, and generally lower overall cost.

In the drawings:

FIG. 1 is a longitudinal sectional view taken through one embodiment of the invention.

FIG. 2 is a transverse sectional view taken on line 22 in FIG. 1.

General arrangement The illustrated device is in the nature of a fluid compressor 10 especially suited for use in small size refrigeration systems, as for example home air conditioners. The general design features could also be employed in other pumps such as air compressors and water pumps.

In the illustrated refrigeration environment the compressor is provided with an inlet fitting 24 connected to the suction line coming from the evaporator, and a compressed gas outlet 25 leading to the condenser. The systern may be initially charged with refrigerant, such as Freon F-22, at a sufficient pressure to maintain a body of liquid in the compressor during periods of service and shutdown. The compressor may be positioned as the lowest gravitational point in the system to insure retention of liquid therein; alternatively a check valve may be located in the suction line to preclude backflow out of the compressor housing. If desired the compressor liquid may be a non-refrigerant such as an oil or some other higher boiling point refrigerant. The compressor liquid should preferably be relatively non-viscous to eliminate shear losses; it should also have a high specific gravity for maximum kinetic energy transfer to the gas to be compressed.

The compressor includes a liquid impeller Wheel 38 which centrifugally pumps liquid from the lower portion of the compressor housing outwardly and then upwardly along the housing outer periphery in annular passage 86. As the liquid is pumped out of wheel 38 it entrains gas from chamber 22 which is connected with gas inlet 24. The liquid thus imparts kinetic energy to the gas particles so that the gas enjoys a compressed state when it reaches the chamber space 88 just below outlet 25. The gas may be discharged through outlet 25, while the liquid is drawn back through an auxiliary impeller wheel 60 for pressure elevation and subsequent return to wheel 38.

Structural details Compressor 10 comprises an upright tubular housing 12 having a bottom end wall 14, cylindrical side wall 16 and top wall 18. Projecting downwardly from wall 14 is a cylindrical cup-like wall structure 20 which forms an inlet chamber 22 for refrigerant gas coming from a conventional evaporator through a tubular fitting 24. Gas passes from chamber 22 upwardly through openings 26 in an internal housing structure 28.

Structure 28 comprises an annular upstanding side wall 30, radial bottom wall 32, and cup-like sub-housing 34. An O-ring seal 36 isolates the space between walls 14 and 32 from chamber 22, thus causing the gas to move through openings 26 and against the lower end face of a rotary liquid impeller wheel 38. Wheel 38 comprises a hub portion 40, a lower end wall 42, eight backwardly curved vanes 43 formed integrally with wall 42, and an upper end wall 44 formed separately from wall 42. Hollow rivets 45 secure wall 44 against vanes 43, thus permitting some of the inlet gas to possibly proceed through the rivets to the space above end wall 44. It will be noted that the upper and lower faces of wheel 38 are engaged with the edges of two sealing rings 47 and 49. These rings are urged by springs 51 against the impeller wheel to prevent liquid from bypassing the wheel interior.

Impeller 38 is powered by an electric motor 46 com prising a laminated stator 48 having windings 50, and a laminated rotor 52 having windings 54. Rotor 52 is carried on a shaft 56 which is journaled in sleeve bearings 58 carried by the upstanding tubular portion 61 of a motor support 62. Tubular portion 61 is connected to the main body portion of the motor support by four relatively thin ribs or struts 65, the spaces therebetween serving to conduct liquid from space 66 into the inlet eye of wheel 38. The motor is held down by two or more screws 64 threaded into support 62. The motor support may in turn be held down by screws or rivets 71 (FIG. 2) going through walls 14 and selected ones of vanes 87 formed integrally with support 62, as by die casting.

Liquid is delivered to space 66 by means of the vaned impeller wheel 60 secured to the upper end of rotor shaft 56. The wheel is housed within a chamber having an upper wall 63 formed as part of a cup-shaped sub-housing 57, said sub-housing having an axially extending inlet wall 67, an outwardly radiating Wall 69 and a generally axially extending annular wall 70 telescoped onto the periphery of motor support 62. The sub-housing 57 may be positioned within the compressor by means of a spider structure 72 having an outer annular wall 74, inwardly radiating arms 76, and inner annular split ring 78. A rubber annulus 80 may be interposed between ring 78 and wall portion 67. Underlying impeller 60 is a chamber wall 82 having an axially extending peripheral portion 84 telescoped over the outer periphery of the motor.

Assuming a sufficient quantity of liquid iri space 66, rotation of impeller 38 will centrifugally pump liquid from space 66 into the outwardly radiating diffusion passageway 84 formed between wall 32 and the lower face of motor support 62. As the liquid is thrown into passageway 84 it will entrain gas from chamber 22. Passageway 84 preferably has a gradually increasing vertical cross section as it radiates outwardly; additionally the increasing diameter of the passageway will increase the flow area. As a result, there will be a gradual dilfusion or slowing down of the liquid-gas mixture as the mixture moves outwardly in passageway 84. The more gradual the deceleration the less will be the turbulence engendered in thefluid stream. The deceleration will be accompanied by a transfer of kinetic energy from the liquid to the gas. Passageway 84 may be provided with fluid-straightener vanes 87, preferably cast integrally with motor support 62. These vanes are especially useful in the illustrated annular discharge passageway where no other obstruction is present to avoid continuous swirling of the fluid. The depth of the vanes accurately determine the vertical dimension of passageway 86.

As the gas-liquid mixture reaches the outer periphery of passageway 84 it is gradually turned upwardly into the annular axially extending passageway 86. This passageway increases in cross section so that the gas-liquid mixture undergoes a further deceleration as it moves upwardly in the passageway. By the time the gas-liquid mixture has reached the upper end of passageway 86 a great deal of the velocity pressure will have been transformed into static pressure. The gas will thus have an increased energy-pressure level as it separates from the liquid in the chamber generally designated by numeral 88.

The spent liquid floods the space above inlet 67 and thus constitutes a liquid source for impeller 60. The liquid is drawn into inlet 67 by rotation of impeller 69, and is discharged into the annular outwardly radiating duct 90 formed between walls 69 and 82. This annular duct has a gradually increasing cross section as it radiates outwardly so that the liquid diffuses and decelerates as it moves outwardly in the duct. The liquid will be turned downwardly by the curved wall portion joining walls 69 and the liquid will thus be forced into the axially extending dilfusion duct 92. It will be seen that duct 92 has a gradually increasing cross section as it moves downwardly, thus further diffusing and decelerating the liquid. The gradual diffusion process will convert the velocity pressure into static pressure so that the liquid in space 66 will have a high static head as it is introduced into the impeller wheel 38. This high static inlet head will cooperate with the velocity of wheel 38 in providing a high radial velocity out of the wheel 38 periphrey. Such a high radial velocity will cause entrainment of increased quantities of gas, and will produce high energy transfer from the liquid to the gas as the gas is moved outwardly in passageways 84 and 86.

Features of the invention A dominant feature of the invention is the use of two impellers 38 and 60, one of which acts as a fluid-entrainment impeller, and the other of which acts as a pressure elevation means for the liquid recirculated back to the entraining impeller. This two-impeller arrangement advantageously provides higher liquid velocities out of the fluidentraining impeller, increased entrainment of fluid, greater energy exchange with the fluid, and higher output pressures.

An auxiliary feature of some importance is the ability of impeller 60 to function as a gas-liquid separator. Thus, during service the impeller will act on the fluid mixture above inlet eye 67 so that the heavier liquid will centrifuge toward the outer annular space within eye 67. The tightly swirling lighter gas will be crowded into the inner annular portion within or above the eye 67. A swirling gas vortex above the eye will be maintained adjacent the discharge fitting 25. Liquid will predominate in eye 67, with little or no gas being allowed to enter the eye and impeller. The tightly swirling gas above the eye will cooperate with gravitational effects to preclude any substantial liquid flow into discharge fitting 25.

A feature of considerable importance is the illustrated use of diffusion passageways and diffusion ducts for converting velocity pressures into static pressures, without excessive turbulence losses which would deleteriously affect the energy transfer. The annular nature of these ducts and passageways is believed to contribute toward non-turbulent diffusion and satisfactory flow capacity while keeping the overall dimension of the compressor fairly small. It will also be noted that the diffusion passageways and dilfusion ducts are relatively long and are advantageously nested one within another in concentric relation so as to further contribute toward pressure conversion without incerasing the overall housing dimension.

Manufacture of the pump is facilitated by the fact that internal housing 28 and motor support 62 can be secured together as a sub-assembly by screws 71. Prior to forming this sub-assembly, the motor may be mounted on support 62 and the impeller 38 mounted on impeller shaft 56, the construction being such that the radial and axial alignment of the impeller discharge with passage 84 may be readily and directly checked. Thereafter housing 28 may be secured to motor support 62 to complete the sub-assembly. The entire sub-assembly can then be inserted into housing 12 and supported on large O-ring 36; no rivets, screws etc. are believed necessary between housings 28 and 12. The final assembly operation includes the installation of spider 72 into the upper portion of housing 12.

It will be noted that in the completed assembly the electric motor and its support structure are isolated from housing 12 by two rubber elements 36 and 80. These elements are employed to dampen motor hum and thus improve the attractiveness of this pump for certain air conditioner applications where noise may be a consideration.

Some variation in structure and arrangement may of course be resorted to without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. A fluid pump comprising a housing confining a mass of liquid therewithin; a motor disposed within the housing, said motor having a double-ended shaft extending therethrough; a first pressure-elevation impeller aflixed to one end of the motor shaft and operable to pump the confined liquid by centrifugal action; a second impeller affixed to the other end of the motor shaft and having an inlet located to receive high pressure liquid from said first impeller; said first impeller discharging liquid to the second impeller through an annular diffusion duct initiating at the outer periphery of the first impeller; said diffusion duct including a first annular duct portion radiating outwardly from the first impeller periphery, and a second annular duct portion extending axially toward the second impeller in the space surrounding the motor; a passageway connecting the outlet of the second impeller with the inlet of the first impeller, whereby to effect recirculation of the liquid within the pump housing; a source of fluid connected with said passageway, whereby the liquid flowing through said passageway causes fluid to be entrained in the liquid stream; means allowing the entrained fluid to separate from the entraining liquid; and means for discharging the separated fluid from the pump.

2. The fluid pump of claim 1 wherein the housing is a tubular housing; said motor having its shaft located on the housing axis; the aforementioned passageway comprising an annular diffusion passageway which radiates outwardly from the second impeller periphery and thence axially along the outer surface of the aforementioned diffusion duct; said fluid source comprising a fluid chamber disposed adjacent an end surface of the second impeller in limited communication with the second impeller periphery, whereby liquid discharged from the second impeller entrains fluid as it leaves the impeller periphery.

3. The fluid pump of claim 2 wherein the housing and motor are oriented so that the shaft is substantially vertical; said first impeller being located on the upper end of the shaft, and said second impeller being located on the lower end of the shaft.

4. The fluid pump of claim 1 wherein the pump housing is tubular; a sub-assembly within the pump housing comprising the aforementioned motor having its shaft located on the pump housing axis; said first impeller being provided with an impeller housing which includes an inlet eye wall structure formed as part of said sub-assembly; first elastomeric means peripherally engaging the inlet eye wall structure to assist in cushionably isolating the subassembly from the pump housing; the aforementioned passageway comprising an annular diffusion discharge passageway which includes a generally cup-shaped internal housing formed as part of the aforementioned sub-assembly; and second elastomeric means interposed between said internal housing and pump housing to cooperate with the first elastomeric means in cushionably isolating the sub-assembly from the pump housing.

5. The fluid pump of claim 4 wherein the sub-assembly further includes a motor support positioned within the cup-shaped internal housing; said motor support having integrally formed projections engaging the inner surface of the internal housing to accurately define the cross sectional dimension of the diffusion passageway.

6. A fluid pump comprising a housing confining a mass of liquid therewithin; a first pressureelevation impeller operable to pump the confined liquid by centrifugal action; a second impeller receiving high pressure liquid discharged from said first impeller and pumping same back i to the first impeller; the discharge from said second impeller comprising an annular diffusion passageway having a first annular portion radiating outwardly from the second impeller periphery, and a second annular portion extending from the first portion axially toward the first impeller; a source of fluid communicating with the diffusion passageway whereby the liquid flowing therethrough causes fluid to be entrained in the liquid stream; means allowing the entrained fluid to separate from the entraining liquid without entering the first impeller; and means for discharging the separated fluid from the pump.

7. The fluid pump of claim 6 wherein the first impeller discharges into an annular diffusion duct having a first annular duct portion radiating outwardly from the first impeller periphery, and a second annular duct portion extending axially toward the second impeller; said second duct portion being disposed within the second portion of the aforementioned annular passageway.

8. The fluid pump of claim 7 wherein the inner wall of the second portion of the annular passageway constitutes the outer wall of the second portion of the annular duct.

9. The fluid pump of claim 7 and further comprising fluid-straightener vanes located in the first portion of the annular passageway for removing circumferential swirl from the fluid discharged from the second impeller.

References Cited UNITED STATES PATENTS 1,009,908 11/1911 Lafore 230108 1,148,992 8/1915 Scaver 230108 2,533,028 12/1950 McConaghy 10355 3,081,932 3/1963 De Lancey 230-408 HENRY F. RADUAZO, Primary Examiner. 

